Differential Diagnosis
- Single Most Likely Diagnosis
- Pyelonephritis: The patient presents with left flank pain, elevated CRP (23.4), and an elevated white blood cell count (WBC 13.8) with a predominance of neutrophils (seg neut absolute 11.9). These findings, along with the mild anemia (hemoglobin 11.9) and normal kidney function (BUN 5), suggest an infectious process such as pyelonephritis, which is an infection of the kidney.
- Other Likely Diagnoses
- Nephrolithiasis (Kidney Stones): The left flank pain could be indicative of a kidney stone, which might also cause an inflammatory response and thus an elevated CRP. However, the absence of significant hematuria or more specific symptoms like severe, colicky pain makes this less likely than pyelonephritis.
- Musculoskeletal Pain: The flank pain could have a musculoskeletal origin, but the laboratory findings (elevated WBC, CRP) suggest an underlying inflammatory or infectious process rather than a purely musculoskeletal issue.
- Do Not Miss Diagnoses
- Sepsis: Although the patient's vital signs are not provided, the elevated WBC and CRP could indicate a systemic infection. Sepsis is a life-threatening condition that requires immediate recognition and treatment. The presence of any signs of organ dysfunction (e.g., altered mental status, significant hypotension) would increase the suspicion for sepsis.
- Appendicitis (if the pain radiates or is referred to the flank): Although less common, appendicitis can sometimes present with flank pain, especially if the appendix is retrocecal. The elevated WBC and CRP would support this diagnosis, but the location and character of the pain would be critical in distinguishing it from other causes.
- Perinephric Abscess: This is a collection of pus in the tissue around the kidney and can present with flank pain and signs of infection like fever and elevated WBC. It's a serious condition that requires prompt diagnosis and treatment.
- Rare Diagnoses
- Vasculitis (e.g., ANCA-associated vasculitis): This could present with systemic inflammation (elevated CRP, WBC) and flank pain due to renal involvement. However, it would typically be accompanied by other systemic symptoms and specific autoantibodies.
- Renal Infarction: This is a rare condition where the blood supply to the kidney is interrupted, leading to tissue death. It can present with acute flank pain and elevated inflammatory markers but is less likely given the absence of specific risk factors (e.g., atrial fibrillation, thrombophilia) or more typical symptoms like severe, sudden-onset pain.